Shaft seal



March` 16, 1943. l

SHAFT SEAL Filed Dec. .50; 1941 L. P. GROBL "y His Attor'ney.

,Ptenred Mgr. 18, 1943 .Lloyd P. Grobel, Schcnectady, N.

Y., assignor to General Electric Company, a corporation of New YorkAppucann December 30, 1941, serial No. 424,899

1 Claim.

My invention relates to shaft seals and particularly to liquid filmseals used for preventing the escape of gas between a shaft and its.enclosing casin'g.

In gas cooled dynamo-electric machines, an enclosing casing is providedwhich is filled with a ventilating gas such as hydrogen, which iscirculated in the casing and through the machine to ventilate thevarious windings and parts of the machine. Openings are arranged in theends of the enclosing c'asing of the shaft of the machine, and bearingsare arranged adjacent the ends of the enclosing casing to support theshaft and a rotatable member of the machine. In order to prevent theloss of ventilating gas from the enclosing casing by leakage into thesurrounding atmosphere and. to prevent the contamination of theventilating gas in the enclosing oasing by leakage of air thereinto, aseal is provided between the shaft and the enclosing casing adj acenteach of the openings.

An object of my invention isl to provide an improved shaft seal of theliquid film type.

Another object of my invention is to provide an improved seal of theliquid film type for gas a filled dynamo-electric machines forminiinizing the flow of the sealing liquid required to 'provide theseal.

Further' objects and advantages of my inven- -tion willibecome apparentand my invention will be better understood from the followingdescription referring to the accompanying drawing, and [the features ofnovelty which characterlze my invention will be pointed out withparticularity in the claim annexed to and forming part of thisspecification.

In the drawing, Fig. 1 is a side elevational view, partly broken away,of a dynamo-electric 'machine provided with my improved liquid filmseal; and Flig.E 2 is an enlarged view, partly in section of the shaftand shaft seal shown in Fig. 1.

Referring to the drawing, I have shown a dyname-electric machineincluding a stationary member IO and a rotatable member provided with anenclosing casing |2 fllled with a ventilating gas other than air, suchas hydrogen. The v 'rotatable member ll is mounted on a shaft |3 whichextends through end walls |4 of the enclosing casing |2. The shaft |3 issupported. in bearings |5 mounted in bearing housings |6 carried by endwalls H of the'machine 'casing.

In order to ventilate and cool the dynamoelectric machine effectively,the ventilating gas within the enclosing casing 12 is circulated thereifrom the end of the enclosing casing |2 through an opening Il providedin the end of a fan casing 18 surrounding a fan |9 carried by therotatable member I, and the gas is discharged into the air gap betweenthe stationary member Ill and the' rotatable member of thedynamoelectricmachine and into other axial ventilating passages' The ventilating gasthen flows outwardly through a plurality of radially disposed oroutwardly extending ducts 20 arranged between groups of laminations ofthe stationary member IO and into a plurality of passages 2| extendingbetween the ends of the enclosing casing |2 and the stationary memberl0.

A shaft sealing member is provided for the rotatable shaft |3 whichincludes an annular sealing ring member 22 secured to the bearing |5.This annular seal-ing member 22 is formed with an annular chamber orreservoir 23 for supplying sealing liquid under pressure to'a fiuid orliquid seal.- This sealing liquid is supplied to the annular chamber 23from a pressure reservoir by a supply pipe 24 and through a connectingpassage 25 formed in the bearing housing 16 and the bearing |5. Thisconnecting passage 25 extends into communication with the annularchamber 23 and the sealing liquid passes from the chamber 23 into arelatively narrow sealing liquid supply chamber 26 formed with a wa'llon each side thereof which includes a wall 21 which forms part of thebearing |5 and a wall 28 which forms part of the annular sealing member22. On the outer side of eachof these walls 21 and 28 is formed acollecting passage 29 and 30, vre'- spectively, into which sealingliquid is adapted to be collected when it passes between sealingsurfaces of the chamber walls extending about the shaft |3. Each ofthese chambers is provided with a drain passage 3| and 32 which leadinto sumps 33 and 34, respectively, from which the sealing liquid isdrained, cooled, and recirculated.

It is desirable that the amount of sealing liquid passing through theseal should be as small as possible in order to minimize the treatmentof the sealing liquid before it is recirculated through the-Seal. Inmostlarge dynamo-electric machines such as the one illustrated, therotatable member il, including the shaft |3, is adapted to rotate onlyAin a predetermined'direction. In the illustrated arrangement, this isindicated by the arrow 35. The flow of sealing liquid from the sealingliquid pressure chamber 26 is minimized These spiral grooves extend inopposite directions in the two wall sealing surfaces and in a sense suchthat the rotation of the shaft in its predetermined direction tends tocreate a fluid or liquid pressure on the sealing liquid through thespiral grooves which is opposed to the pressure of the sealing fluid inthe supply chamber 26. By properly proportioning these spiral groovesand providing them with the proper pitch, the back pressure towards thefeeding chamber on each side thereof created by rotation of the shaft |3in the liquid in these grooves may be made such that a very minimumamount of liquid passes along the shaft in opposite directions into thecollecting chambers 29 and 30 to assure the proper operation of theseal. A small clearance seal is formedby ungrooved portions 38 and 39 inthe walls 21 and 28, respectively, adjacent the sealing liquid supplychamber 28.

While I have illustrated and described a particular embodiment of myinvention, modifications thereof will occur to those skilled in the art.I desire it to be understood, therefore, that my invention is not to belimited to the particular arrangement disclosed, and I intend in theappended claim to cover all modifications which do not depart from thespirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

A shaft seal for a rotatable shaft arranged to rotate in a predetermineddirection including means having a sealing liquid chamber about saidshaft with a seaiing wall on each side of said chamber for feedingsealing liquid in both directions along said shaft, means for supplyingseali ,from said chamber. a sealing liquid collecting passage on theouter side' of each' of said spiral grooves. an ungrooved'bearingsection on the outer side of each of said collecting passages.

and an ungrooved sealing surface on each of' said chamber walls aboutsaid'shaft adjacent said chamber.

LLOYD P; GROBE'L.

